New mobile phone technology has rendered Tony Blair's pledge to bring street crime under control meaningless, say the Conservatives.

The attack came as Downing Street appeared to play down the prime minister's promise - saying it wanted to stop the "upward trend" before bringing the numbers down.

I find it staggering that the prime minister was willing to take the credit for a change in technology that would have led to a cut in crime

Richard BarnesTory spokesman

Mr Blair told MPs on Wednesday that London's sharp rise in street robberies would be brought under control within five months.

Now Number 10 has said the prime minister was only building on a pledge the government made in February to tackle crime on London's streets within six months.

The government says it is focusing its efforts on the 10 areas where people are 80% more likely to be mugged.

Although Home Secretary David Blunkett later said that he did not believe failure to meet the deadline should amount to a resigning matter.

But he insisted the government would tackle street crime as they had tackled burglary and vehicle crime after 1997.

"[Street crime] applies everywhere, but we're targeting the 10 most difficult areas where over 80% of street crime currently occurs and I think most people would expect
us to do that," he said.

Richard Barnes, the Conservatives' crime spokesman in London and deputy chairman of the Metropolitan Police Authority, accused Mr Blair of "fiddling the figures".

'Staggering'

The Metropolitan Police expect new technology, which disables stolen mobile phones, to come into service in late July or early August, said Mr Barnes.

A similar move in Amsterdam led to a 42% fall in street crime within six weeks.

"I find it staggering that the prime minister was willing to take the credit for a change in technology that would have led to a cut in crime," added Mr Barnes.

Mr Duncan Smith went on the attack in the Commons

Other critics say there is bound to be a fall in September compared to last year, when the month saw the start of a crime boom as police were diverted to other duties in the wake of the US terror attacks.

Downing Street on Thursday said Mr Blair was not setting new timescales or targets but wanted to halt the rise in street crime and start to cut it.

Mr Blair's spokesman said: "The prime minister is not saying that... nobody will be mugged on the streets of these 10 areas."

But with extra resources, political energy and police effort, he expected to see results by the end of September, when the police's Safer Street's initiative ends.

Tory leader Iain Duncan Smith has written to the prime minister demanding to know why the term "COBRA" was used by officials to describe the crime summit from where the September deadline had originated.

'National crisis?'

COBRA is usually used as a shorthand for meetings to discuss national emergencies, although on this occasion Number 10 insisted the word was merely used to describe the room in which the crime summit took place.

Mr Duncan Smith wrote: "I believe that the last three times [COBRA] met was for the fuel crisis, foot-and-mouth and the war on terrorism.

"Does this now mean that your government accepts that we have a major crisis with the rising levels of street and violent crime and that the police are unable to deal with this on their own?

"I believe that this is a major development."

But Number 10 played down what it said was merely the fourth meeting of the Street Crime Task Force which was held in Cabinet Office Briefing Room A - COBRA.